acceptable range for ΔCt ? - (May/12/2009 )

Hi,

I'm reading a paper that the ΔCt of their experiments goes higher than 20.

in my experiments I barely get ΔCt higher than 10 when I use Beta actin. what is the acceptable range for ΔCt ?

I'm sure it will depend on the set up of your reaction to a degree and the expression of your gene of interest. But I regularly get Ct values in the mid-teens to upper 20s with a starting amount of 200ng in a 20ul reaction. I usually run reactions to 50 cycles, and you can get amplification in the upper 30s even with samples that should be negative for the primers used. Anything up that high is probably nonspecific binding.